Biaxial stretch wrapping

ABSTRACT

Stretch wrapping packaging material on a load includes introducing stretch wrap packaging material onto V shaped tips of projecting portions of a first grooved roller so that the packaging material spans the nonprojecting portions of the first grooved roller. The web of packaging material and the first grooved roller are transported in the direction generally parallel to the grooves. The web of packaging material spanning the nonprojecting portions of the first grooved roller is impinged with V shaped tips of projecting portions of a second grooved roller. The tips of the projecting portions of the second grooved roller are transported at a speed which is less than the speed of the tips of the projecting portions of the first grooved roller. The tips of the projecting portions of the second grooved roller moves at a speed which stretches the web between the first and second grooved surfaces in a direction transverse to the direction in which it is transported and minimizes any stretching of the web in the direction in which the web is transported. The web is stretched between the projecting portions of the first and second grooved rollers in a direction transverse to the direction in which the web is transported. The web is separated from the first and second grooved surfaces and wrapped onto a load by providing relative rotation between the load and a dispensing mechanism for the web.

BACKGROUND OF THE INVENTION

The invention relates to stretch wrapping methods and apparatus whichwrap a load with stretch wrap packaging material.

DESCRIPTION OF THE RELATED ART

Stretch wrapping is a packaging technique which dispenses and wrapspackaging material in a stretched condition around a load to cover andcontain the load.

Early stretch wrapping techniques positioned a load on a turntable andfastened the leading end of a web of stretch wrap packaging material tothe load or the turntable. As the turntable rotated, the roll of filmwas restrained by a brake to stretch the packaging material in thedirection in which it was being dispensed as the packaging material waswrapped around the load. A similar stretch wrapping technique revolved afilm web dispenser around a stationary load to wrap the stretch film webaround the load.

There are a number of factors which are critical to whether a stretchwrapping technique is commercially viable. A first factor is that thetechnique must be reliable. For a stretch wrapping technique to bereliable, it must be successfully repeatable for an extensive period oftime in a commercial environment without failure of the packagingmaterial or other defects which would interrupt the wrapping process. Indesigning a stretch wrapping technique which is reliable in a commercialenvironment, it is necessary to take into account the skill andsophistication of the machine operator, the types of loads being wrappedand the impact of corners and other hostile load conditions on thepackaging material, and the ease of employing the particular stretchwrapping technique.

A second factor for commercial viability of a stretch wrapping techniqueis that the cost of the additional equipment used in the stretchwrapping technique is justified by the value and significance of theadvantages that it provides.

A third factor for commercial viability of a stretch wrapping techniqueis the speed at which the stretch wrapping technique can be performedwhile maintaining the quality of the packaging material. Since currentstretch wrapping techniques permit packaging material to be dispensed,stretched and wrapped on a load at rates exceeding 500 feet per minuteor 60 revolutions per minute it is necessary for any new stretchwrapping techniques which offer additional advantages to be operable atspeeds which are possible with stretch wrapping equipment that iscurrently available.

A fourth factor for commercial viability of a stretch wrapping techniqueis the quality of the packaging material after it has been dispensed,stretched and wrapped on the load. Stretch wrapping techniques which ripor otherwise decrease the integrity or appearance of the packagingmaterial and inhibit its ability to unitize and cover the load aregenerally unacceptable to the industry.

A fifth factor for the commercial viability of stretch wrappingtechnique is its ability to reduce the amount of packaging materialnecessary to wrap a given load. This reduces the cost to wrap each load.It also results in a favorable ecological impact through "sourcereduction," namely, less raw materials are used to make the packagingfor a given load and less packaging material needs to be trashed orrecycled when the load is unwrapped.

A sixth factor for the commercial viability of a stretch wrappingtechnique is to not appreciably weaken the packaging material in thedirection in which it is being dispensed and wrapped on the load. Evenmore preferably, it is desirable that the stretch wrapping techniqueeither maintain or increase the strength of the film in the direction inwhich it is dispensed and wrapped on the load while providing otherbenefits.

A seventh factor for the commercial viability of a stretch wrappingtechnique is flexibility and adaptability of the technique for wrappinga wide variety of load sizes and shapes.

An example of a particularly effective development in stretch wrappingwas a previous invention of Lantech which employed a film web dispenserhaving two closely spaced rollers to stretch a web of packaging materialsubstantially over its yield point in the dispensing direction. Thistechnique was commercially successful for the reasons discussed above.It was reliable due to repeatability without failure in the commercialenvironment. It could be used to wrap a wide variety of loads and couldbe performed at dispensing and wrapping speeds which were used at thetime of the invention. The quality of the wrapping material wasmaintained, and the strength of the wrapping material in the dispensingand wrapping direction was increased while reducing the amount ofwrapping material required below those which were previously possible ina repetitive commercial environment.

After seeing the huge commercial success and impact of this technique ofstretching packaging material in the direction in which it is dispensedand wrapped on a load, efforts were made to develop a stretch wrappingtechnique in which the packaging material could be stretched in adirection transverse to the direction in which it was being dispensedand wrapped on a load. It was hoped that such a development wouldfurther strengthen the packaging material, decrease the amount ofpackaging material needed to cover a load, provide transversecontainment of the load, and provide greater flexibility in adjustingthe width of a single roll of packaging material to accommodate loads ofdifferent widths.

However, until the present invention there was no commerciallyacceptable stretch wrapping technique which could transversely orbiaxially stretch packaging material while wrapping a load. Previoustechniques did not maintain reliability of the operation in a repetitivecommercial environment, attain dispensing and wrapping speeds requiredin commercial applications, maintain the quality of the packagingmaterial required in commercial applications, and maintain or increasethe strength of the packaging material in the direction the packagingmaterial is dispensed and wrapped on a load.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method andapparatus for stretching packaging material in a transverse direction orbiaxially when dispensing and wrapping the packaging material on a loadwhile maintaining the reliability of the wrapping operation in arepetitive commercial environment.

It is also an object of the present invention to provide a method andapparatus for stretching packaging material in a transverse direction orbiaxially when dispensing and wrapping the packaging material on a loadwhile performing dispensing and wrapping of the packaging material atspeeds which are currently being used in the industry and whilemaintaining the quality of the wrapping material.

It is another object of the present invention to provide a method andapparatus for stretching packaging material in a transverse direction orbiaxially when dispensing and wrapping the packaging material on a loadwhile maintaining or increasing strength of the packaging material inthe dispensing and wrapping direction.

It is yet another object of the present invention to provide a methodand apparatus for stretching packaging material in a transversedirection or biaxially when dispensing and wrapping the packagingmaterial on a load while reducing the amount of packaging materialnecessary to wrap a given load.

It is a further object of the present invention to provide a method andapparatus for stretching packaging material in a transverse direction orbiaxially when dispensing and wrapping the packaging material on a loadwhile providing flexibility and adaptability of the techniques forwrapping a wide variety of load sizes and shapes.

It is yet a further object of the present invention to provide a methodand apparatus for stretching packaging material in a transversedirection or biaxially when dispensing and wrapping the packagingmaterial on a load while keeping the cost of the operation and apparatussufficiently low to justify the benefits provided.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

To achieve the foregoing objects, and in accordance with the purposes ofthe invention as embodied and broadly described herein, a process andapparatus are provided for stretch wrapping a load. A sheet of stretchwrap packaging material is introduced onto tips of projecting portionsof a first grooved surface and spans nonprojecting portions of the firstgrooved surface.

The packaging material and the first grooved surface are transported ina direction generally parallel to the grooves. The packaging materialspanning the nonprojecting portions of the first grooved surface isimpinged with tips of projecting portions of a second grooved surface.It is preferable that both the first and second grooved surfaces arecircumferentially grooved roller surfaces. The tips of the projectingportions of the second grooved cylindrical surface are transported at aspeed which is less than the speed of the tips of projecting portions ofthe first grooved cylindrical surface.

The packaging material is stretched between the projecting portions ofthe first and second grooved surfaces in a direction transverse to thedirection in which the packaging material is transported. The packagingmaterial is then separated from the first and second grooved surfacesand wrapped onto a load.

It is preferable that the speed of the tips of the projecting portionsof the second grooved surface are toward the center of a range definedby the tangential speed of the first grooved surface at the radius wherethe tips of projecting portions of the second grooved surface firstimpinge the packaging material and the tangential speed of the firstgrooved surface at the radius where the tips of projecting portions ofthe second grooved surface maximally impinge the packaging material.

It is preferable that the projecting portions of the second groovedsurface are transported at a speed which stretches the packagingmaterial between the projecting portions of the first and second groovedsurfaces in a direction transverse to the direction in which it istransported and minimizes any stretching of the packaging material inthe direction in which the packaging material is transported.

It is preferable to regulate the tension and speed of the packagingmaterial upstream of the first and second grooved surfaces to preventthe packaging material from slipping on the grooved surfaces and toprevent the packaging material from substantially narrowing before beingintroduced onto the projecting portions of the first grooved surface.

It is preferable that the projecting portions of the grooved surfaceshave a V-shaped cross-section. It is preferable that the projectingportions are closely spaced and contact a minimal percentage of theoriginal sheet width between adjacent projecting portions.

It is preferable to also stretch the packaging material in the directionin which it is dispensed and wrapped onto the load in order to biaxiallystretch the packaging material while wrapping it around the load.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention and, together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a top schematic view of a first embodiment of a stretchwrapping apparatus according to the present invention.

FIG. 2 is a side view of FIG. 1.

FIG. 3 is an enlarged view of a portion of FIG. 1.

FIG. 4 is a side view of FIG. 3.

FIG. 5a is an enlarged view of a portion of FIG. 4.

FIG. 5b is an enlarged view of a portion of FIG. 5a.

FIG. 6a is a top view of a first alternative for providing rotationbetween a packaging material dispenser and a load.

FIG. 6b is a side view of a first alternative for providing rotationbetween a packaging material dispenser and a load.

FIG. 7a is a top view of a second alternative for providing rotationbetween a packaging material dispenser and a load.

FIG. 7b is a side view of a second alternative for providing rotationbetween a packaging material dispenser and a load.

FIG. 8 is a top view of a second embodiment of a stretch wrappingapparatus incorporating the teachings to the present invention.

FIG. 9 is a side view of the apparatus shown in FIG. 8.

FIG. 10 is a top view of a third embodiment of a stretch wrappingapparatus incorporating the teachings of the present invention.

FIG. 11 is a side view of the apparatus shown in FIG. 10.

FIG. 12a is a top view of a first alternative to the first embodimentshown in FIG. 1.

FIG. 12b is a first side view of FIG. 12a.

FIG. 12c is an enlarged view of a portion of FIG. 12b.

FIG. 12d is a second side view of FIG. 12a.

FIG. 13a is a top view of a second alternative to the embodiment shownin FIG. 1.

FIG. 13b is a side view of FIG. 13a.

FIG. 13c is an enlarged view of a portion of 13b.

FIG. 14a is a top view of a fourth embodiment of a stretch wrappingapparatus incorporating the teachings of the present invention.

FIG. 14b is a top view of a fifth embodiment of a stretch wrappingapparatus incorporating the teachings of the present invention.

FIG. 15a is a side view of the apparatus shown in FIG. 14a.

FIG. 15b is an enlarged view of a portion of FIG. 15a.

FIG. 16 is a top view of the sixth embodiment of a stretch wrappingapparatus incorporating the teachings of the present invention.

FIG. 17a is a side view of the apparatus shown in FIG. 16.

FIG. 17b is a left end view of the apparatus shown in FIGS. 16 and 17a.

FIG. 17c is a enlarged view of a portion of FIG. 17b.

FIG. 17d is a right end view of the apparatus shown in FIGS. 16 and 17a.

FIG. 17e is an enlarged view of a portion of FIG. 17d.

FIG. 18a is a side view of a seventh embodiment of a stretch wrappingapparatus incorporating the teachings of the present invention.

FIG. 18b is a bottom view of the apparatus shown in FIG. 18a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention as illustrated in the accompanyingdrawings.

According to the present invention, an apparatus is provided for stretchwrapping a load. A first embodiment of a stretch wrapping apparatusaccording to the present invention is shown in FIGS. 1-5.

According to the present invention, the stretch wrapping apparatusincludes a first grooved surface having projecting portions andnonprojecting portions, with the first grooved surface being movable ina direction generally parallel to its grooves. As shown in FIGS. 1-5,the first grooved surface is a first circumferentially grooved roller102 having projecting portions 104 with tips 110, and nonprojectingportions 106. The first grooved roller 102 is mounted on axle 108 forrotational movement centered about axle 108. As a result, the groovedsurface of first grooved roller 102 is movable in a direction generallyparallel to the circumferential grooves defined by projecting portions104 and nonprojecting portions 106.

According to the present invention, the stretch wrapping apparatus alsoincludes a second grooved surface having projecting portions whichextend between the projecting portions of the first grooved surface, andnonprojecting portions in which the projecting portions of the firstgrooved surface extend. The second grooved surface is movable in adirection generally parallel to its grooves. As shown in FIGS. 1 and 2,the second grooved surface is a second circumferentially grooved roller202 having projecting portions 204 with tips 210, and nonprojectingportions 206. The second grooved roller 202 is mounted on axle 208 forrotational movement centered about axle 208. As a result, the groovedsurface of second grooved roller 202 is movable in a direction generallyparallel to the circumferential grooves defined by projecting portions204 and nonprojecting portions 206.

According to the present invention, means are provided for orienting asheet on the projecting portions of the first grooved surface beforeimpinging the sheet with projecting portions of the second groovedsurface. As shown in FIGS. 1 and 2, the means for orienting a sheetinclude rollers 150 and 152 which define the path of stretch wrappackaging material 154 from roll 156.

Stretch wrap packaging material 154 is preferably a sheet in web formand is preferably one of the stretchable, orientable commerciallyavailable thermoplastic materials designed and sold for stretch wrappingoperations.

According to the present invention, means are provided for transportingthe projecting portions of the second grooved surface at a speed whichstretches the sheet between the projecting portions of the first andsecond grooved surfaces in a direction transverse to the direction inwhich it is transported and minimizes any stretching of the sheet in thedirection in which the web is transported. The grooved surfaces arpreferably transported at relative speeds which align the force lines inthe sheet in a direction substantially transverse to the direction inwhich the sheet is conveyed.

As shown in FIGS. 1 and 2, the means for maintaining the speeds of thegrooved surfaces preferably includes a controllable fixed ratio drivemechanism 157 having sprockets 158 and 160 of fixed relative diametersattached to grooved rollers 102 and 202, an endless chain 162 engagingsprockets 158 and 160, and a motor 164 with motor controller 166 forcontrollably driving endless chain 162. A motorless chain linked driveunit or a pair of commonly controlled motors also may be used to achievea fixed ratio between the speeds of the first and second groovedsurfaces.

According to the present invention, means are provided for maintainingthe tips of the projecting portions of the second grooved roller at aspeed which is less than the speed of the tips of the projectingportions of first grooved roller.

Referring to FIGS. 3-5, drive mechanism 157 maintains the tips 210 ofthe projecting portions 204 of second grooved roller 202 at a speedwhich is less than the speed of the tips 110 of the projecting portions104 of first grooved roller 102. It is preferable that drive mechanism157 maintain the tangential speed V₂ of the tips 210 of the projectingportions 204 of the second grooved roller 202 substantially within andtoward the center of the range between the tangential speed V₁ of thefirst grooved roller 102 at the radius R₁ where the tips 210 ofprojecting portions 204 of the second grooved roller 202 first impingethe packaging material 154 and the tangential speed V_(r) of the firstgrooved roller 102 at the radius r where the tips 210 of projectingportions 204 of the second grooved roller 202 maximally impinge thepackaging material 154. By maintaining the speed in this range, anystretching of the sheet in the direction in which it is transported isminimized throughout the transverse stretching operation andparticularly both at minimal and maximal impingement of the sheet by theprojecting portions.

As shown in FIGS. 3 and 4, and as expressed by the following equations,it is preferable that the speed V₂ of the tips 210 of the projectingportions 204 of the second grooved roller 202 is approximately one halfthe speed V₁ of the tips 110 of projecting portions 104 of the firstgrooved roller 102, times the sum of the radius R₂ of the projectingportions 204 of the second grooved surface 202 over the radius R₁ of theprojecting portions 104 of the first grooved surface 102, and the radiusR₂ of the projecting portions 204 of the second grooved surface 202 overthe difference between the center distance CD of the grooved rollers 102and 202 and the radius R₂ of the projecting portions 204 of the secondgrooved roller 202. It is seen from FIGS. 3-5 that r represents thedifference between the center distance CD of grooved rollers 102 and 202and the radius R₂ of the projecting portions 204 of the second groovedsurface 202. ##EQU1##

According to the present invention, the first and second groovedsurfaces, orienting means and movement maintaining means define adispensing means. As shown in FIGS. 1 and 2, the dispensing meansincludes a dispenser 100 for stretch wrapping packaging material 154.

According to the present invention, the stretch wrapping apparatusincludes means for providing relative rotation between the dispensingmeans and a load to wrap the packaging material around the load. Asshown in FIGS. 1 and 2, the means for providing relative rotationbetween packaging material dispenser 100 and the load 101 includes aturntable 168 which supports load 101, a base 170 on which turntable 168is rotatably mounted and a motor drive system 172 for rotating theturntable 168 relative to packaging material dispenser 100.

As shown in FIGS. 6a and 7a, the means for providing relative rotationbetween the dispensing means and a load can be either the alternativeshown in FIGS. 6a and 6b of a rotatable turntable which rotates the load101a relative to a stationary packaging material dispenser 100a, or thealternative shown in FIGS. 7a and 7b of rotating a packaging materialdispenser 100b around a stationary load 101b. As shown in FIGS. 6 and 7,the axis A of relative rotation between the load and the dispenser forthe packaging material may be in the vertical direction, such as in theunitization of pallet loads. Alternatively the axis of relative rotationmay be in the horizontal direction such as in the bundling of packagesmoving on a horizontal conveyor belt, as shown for example in U.S. Pat.No. 4,866,909 which is incorporated herein by reference. The packagingmaterial is preferably dispensed and wrapped onto the load in acondition in which it is stretched or tensioned in the direction inwhich the packaging material is transported and dispensed.

As shown in FIG. 4 and 5, it is preferable that the area of theprojecting portions 104 and 204 of grooved rollers 102 and 202 on whichthe sheet rests during stretching have flat sides 112 and 212 which giveprojecting portions 104 and 204 a generally V shaped cross section. Theflat sides forming a V shaped cross section are preferable, in contrastto projecting portions having either a convexly curved sinusoidal shapedcross section or a U shaped cross section.

It is preferable that sides 112 and 212 of projecting portions 104 and204 converge outwardly at an angle in the range of about 5 to 90 degreesand even more preferably in the range of about 10 to 20 degrees. It ispreferable to use projecting portions having a slender profile asopposed to projecting portions having a fat or wide profile.

It is preferable that projecting portions 104 and 204 are configured tocontact and support less than about 20 percent, more preferably lessthan about 15 percent, and even more preferably less than about 10percent, of the original sheet width between corresponding points ofadjacent projecting portions 104 at maximal impingement I_(max). Thisleaves the substantial remaining portion of the sheet width unsupportedand available for stretching in the transverse direction.

It is preferable that the pitch of the rollers, namely the distance dbetween adjacent tips 110 of roller 102, and the distance d betweenadjacent tips 210 of roller 202, is in the range of about 1/8 to 1/2inches and even more preferably in the range of about 1/4 to 3/8 inches.

The term tip sharpness radius t of the tip for tips 110 and 210 is usedto describe the general size and sharpness of the tip and is the radiusof curvature at the tip or distance from a point that is of equaldistance from the sidewalls and apex of the projecting portion as shownby the location of the crosses in FIG. 5.

It is preferable that the tip sharpness radius of projecting portions104 and 204 is as sharp as possible without cutting the packagingmaterial when in operation, and preferably is in the range of inches1/128 to 1/16 inches and even more preferably in the range of 1/64 to1/32 inches.

It is preferable that the tip sharpness radius t of the tips 110 and 210are in the range of about 3 to 33 percent, and even more preferablyabout 6 to 12 percent of the pitch or distance d between the tips 110 ofthe projecting portions 104 of first grooved roller 102.

It is preferable that the maximal impingement I_(max) as shown in FIG. 4is in the range of about 1/8 to 1 inch, and even more preferably about1/4 to 1/2 inch.

It is preferable that the maximal impingement I_(max) is substantiallygreater than, and even more preferably in the range of at least abouttwice the distance between the tips 110 of the projecting portions 104on grooved roller 102.

Currently, it is preferably to construct grooved rollers 102 and 104 bymachining circumferential grooves onto nylon cylinders which are forcefit onto metal shafts. The surfaces of the circumferentially groovedrollers preferably have a smooth finish. Alternative constructionmethods include casting the rollers in a grooved shape, or assembling aseries of fixed or floating disks on a keyed shaft.

A currently preferred embodiment uses two identical machined nylonrollers which have an outside radius R of 3 inches. Each roller has a1/4 inch pitch or distance d between the tips of its projectingportions. The tip sharpness radius t of the tips of the projectingportions is 1/64 inches. The projecting portions have flat side whichconverge outwardly at an angle a of 10%. The maximal impingeme I_(max)is 1/2 inches and the projecting portions contact 12 percent of theoriginal sheet width at maximal impingement. The 1/4 inch width of thesheet between adjacent tips on a roller is stretched to 3/4 inches or300% of its original width.

It is preferable to provide means for regulating the tension and speedof the packaging material 154 upstream of the first and second groovedrollers 102 and 202 to prevent the packaging material 154 from slippingon the surface of grooved rollers 102 and 104 and to prevent thepackaging material 154 from substantially narrowing before beingintroduced onto the projecting portions 104 of the first grooved roller102. As shown in FIGS. 1 and 2, the means for regulating the tension andspeed of the packaging material include rollers 150 and 152 whichrestrain the web 154 to accomplish these functions. Rollers 150 and 152can be attached to a frictional braking device or be mechanicallyconnected to the drive train 157 connecting grooved rollers 102 and 202.Alternatively, the means for performing the function of regulating thetension and speed can be an additional stretching system or a brake onfilm roll 156 or a similar mechanism.

It is currently preferable to minimize the distance between theregulating means and the first grooved roller 102 to prevent substantialnarrowing of the packaging material. A currently acceptable distance isabout 11/2 inches.

It is preferable that the stretching wrapping apparatus include a meansfor spreading the web in the transverse direction after stretching theweb in the transverse direction. It is preferable that this spreadingmeans include a bowed roller 174 mounted to rotate about a fixed curvedaxis.

According to one aspect of the present invention, means are provided forvariably controlling the maximum impingement I_(max) of the first andsecond grooved surfaces As shown in FIGS. 2 and 5a, the means forvariably controlling the maximum impingement is control mechanism 191which adjusts and sets the distance between the journals for the firstand second grooved surfaces 102 and 202 and thus controls the centerdistance CD and maximum impingement I_(max) The control mechanism 191 ispreferably located on the journals on both sides of the first and secondgrooved surfaces 102 and 202. Depending on the desired cost, the controlmechanism 191 can be as simple as manually actuated clamps or screwswhich connect the journals and frame, or an automated motor controlsystem which automatically set the spacing between the journals.

The ability to control the maximum impingement I_(max) permits a stretchwrapping apparatus to control and vary the dispensed width of packagingmaterial from a single roll of packaging material having a given width.

According to one aspect of the present invention, an apparatus isprovided for stretch wrapping a load with packaging material which isbeing biaxially stretched as it is being dispensed and wrapped on aload. As shown in FIGS. 8 and 9, the stretch wrapping apparatus includesa first grooved surface which is preferably a first circumferentiallygrooved roller 302, similar to the first grooved roller 102 describedabove. First grooved roller 302 has projecting portions andnonprojecting portions and rotates so as to be movable in a directiongenerally parallel to its grooves.

The stretch wrapping apparatus also includes a second grooved surfacewhich is preferably a second circumferentially grooved roller 402,similar to grooved roller 202 described above. Second grooved roller 402has projecting portions which extend between the projecting portions ofthe first grooved roller and nonprojecting portions in which theprojecting portions 304 of the first grooved roller 302 extend. Thesecond grooved roller 402 rotates so as to be movable in a directiongenerally parallel to its grooves.

Means are provided for orienting packaging material on the projectingportions of the first grooved roller 302 before impinging the packagingmaterial with projecting portions 404 of the second grooved roller 402.As shown in FIGS. 8 and 9, the orienting means is preferably a roller350 which directs the path of the stretch wrap packaging material 354.

Means are provided for maintaining the movement of the tips of theprojecting portions of the second grooved roller 302 at a speed V₂ whichis relative to the speed V₁ of movement of the tips of the projectingportions of the first grooved roller 302 as described above for theapparatus shown in FIGS. 1 and 2. As shown in FIGS. 8 and 9, themaintaining means includes sprockets 358 and 360 attached to rollers 302and 402 coupled by chain drive 362 to motor 364 and motor controller366. These components operate in a manner similar to the correspondingcomponents shown in FIGS. 1 and 2, and serve to maintain the relativerotation of first grooved roller 302 and second roller 402 at a selectedrelative velocity.

According to the invention, means are provided for transporting thepackaging material and for stretching the packaging material in thedirection in which it is transported. The means for stretching thepackaging material in the direction in which the packaging material istransported may alternatively be positioned upstream or downstream ofthe means for stretching the packaging material in the directiontransverse to the direction in which the packaging material istransported. Therefore the step of stretching in the direction in whichthe packaging material is transported may be performed either before orafter the steps of stretching in the direction transverse to thedirection in which the packaging material is transported.

As shown in FIGS. 8 and 9, the means for stretching the web in thedirection in which the web is transported includes an upstream roller450 and a downstream roller 452 which is closely spaced to upstreamroller 450. Rollers 454, 456 and 350 maintain web 354 in position arounda sufficient percentage of the circumference of rollers 450 and 452 toprevent to web from slipping on those rollers 450 and 452. The surfacesof rollers 450 and 452 may be a suitable nonslip substance such as acoating made of a vinyl plastisol which has been foamed and machined asdescribed in U.S. patent application Ser. No. 07/289,442.

The stretch wrapping apparatus also includes means for maintaining thespeed of downstream roller 452 at a speed which is greater than thespeed of the upstream roller 450. It is preferable that upstream anddownstream rollers 450 and 452 are maintained at a constant relativevelocity and are closely spaced to each other to prevent the packagingmaterial from substantially narrowing while being stretched. Preferably,roller 450 includes sprocket 388 and roller 452 includes sprocket 390which are coupled together for relative rotation by chain drive 362which also couple rollers 450 and 452 to rollers 302 and 402.Alternatively the maintaining means may include a motorless chain linkeddrive unit or a pair of commonly controlled motors

According to an aspect of the present invention, after stretching thepackaging material in the direction that it is being transported, it ispreferable to reduce the force and elongation on the packaging materialin that direction before introducing the packaging material onto thetips of the projecting portions of the first grooved surface forstretching in the transverse direction. The force and elongation on thepackaging material as it is introduced on the first grooved surfaceshould be sufficiently high for traction on the projecting portions ofthe first grooved surface and not so high as to tear the packagingmaterial on the tips of the first grooved surface or cause excessiveneckdown of the packaging material.

The stretch wrapping apparatus also includes means for providingrelative rotation between the dispensing means which includes thecomponents of dispenser 300, and a load 301 to wrap the packagingmaterial 354 around the load 301. As shown in FIGS. 8 and 9, the meansfor providing relative rotation include a turntable 368 which is drivenby motor 372 to rotate about base 370, rotating the load 301 relative tothe dispenser 300 for packaging material 354. As discussed in relationto FIGS. 6 and 7, either the load may rotate relative to the dispenseror the dispenser may rotate around the load.

In FIGS. 8 and 9, means are provided to spread the web in the transversedirection after stretching the web in the direction in which it isdispensed It is preferable that the spreading means includes a bowedroller 374 which rotates about a curved fixed axis and is driven by thechain drive which drives the other rollers.

FIGS. 10 and 11 show an alternate embodiment to that shown in FIGS. 8and 9. Corresponding numerals are used to designate correspondingelements. In the embodiment shown in FIGS. 8 and 9, the packagingmaterial is stretched in the dispensing direction before it is stretchedin the transverse direction. In the embodiment shown in FIGS. 10 and 11,the packaging material is stretched in the dispensing direction after itis stretched in the transverse direction.

According to an aspect of the present invention, it is preferable tostretch the packaging material over its yield point in the directiontransverse to the direction in which it is being dispensed toplastically deform the packaging material in the direction transverse tothe direction in which the packaging material is being dispensed.According to another aspect of the present invention, it is preferableto stretch the packaging material over its yield point in the directiontransverse to the direction in which it is being dispensed and in thedirection in which it is dispensed to plastically deform the packagingmaterial both in the direction transverse to the direction in which itis being dispensed and in the direction in which it is dispensed.

Various corner compensating devices such as dancers bars and speedcontrol devices may be used in some applications of the invention. Forexample, a load cell may be used to monitor the force exerted on thepackaging material by the load and the output of the load cell can beused to vary the speed of the motor driving the stretching devices tovary the supply speed of the packaging material in accordance with thedemand speed for the packaging material.

According to an aspect of the present invention, means may be providedto separate the sheet from one of the grooved surfaces. As shown in FIG.12, the separating means preferably include a series of belts 103a whichcirculate around a grooves in tips 110a of projecting portions 104a, anda roller 105a. Other delaminating means include combs and rollers whichassist in removing the web from the upstream roller.

According to an aspect of the present invention, the second groovedsurface includes a plurality of surfaces which sequentially impinge thepackaging material spanning the nonprojecting portions of the firstgrooved roller to increasing extents. As shown in FIG. 13, the pluralityof second grooved surfaces include roller 202b₁ which impinges thepackaging material a given distance below the tips of the projectingportions of first grooved roller 102b. Subsequently roller 202b₂impinges the packaging material even farther than the packaging materialwas impinged by roller 202b₁.

According to an aspect of the present invention, one of the first andsecond grooved surfaces is a convex side of a cylinder and a portion ofthe other is a segment of a concave side of a cylinder. As shown in FIG.14a, the first grooved surface includes an endless belt 502 whichrotates about rollers 503 and 505. As shown in FIG. 15b, the groovedendless belt 502 includes projecting portions and nonprojectingportions. As shown in FIGS. 14a, roller 550 acts as a means fororienting the sheet 554 on the projecting portions of first groovedsurface, grooved endless belt 502, before impinging sheet 554 withprojecting portions of the second grooved surface, grooved roller 602.Roller 551 acts as a means for maintaining sheet 554 on the projectingportions of first grooved surface, grooved endless belt 502, after sheet554 is no longer impinged with the projecting portions of the secondgrooved surface, grooved roller 602.

FIG. 14b is an alternative to the embodiment shown in FIG. 14a. As shownin FIG. 14b, the first grooved surface includes grooved rollers 602bhaving projecting portions and non-projecting portions similar to roller602 in FIG. 14a. The second grooved surface includes an endless belt502b, similar to endless belt 502 in FIG. 14a, which rotates aboutrollers 503b and 505b. Roller 550b acts as a means for orienting thesheet 554b on the projecting portions of first grooved surface, groovedroller 602b, before impinging sheet 554b with projecting portions of thesecond grooved surface, grooved endless belt 502b Roller 551b acts as ameans for orienting the sheet 554b on the projecting portions of groovedroller 602b after sheet 554b is no longer impinged by grooved endlessbelt 502b.

The shape of the projecting portions and the impingement relationshipsof the embodiments shown in FIGS. 14 and 15 are preferably the same asthose in the embodiment shown and described in relation to FIGS. 1-5which uses two grooved rollers. It is preferable to transport theprojecting portions of the second grooved surface at a speed whichstretches the web between the projecting portions of the first andsecond grooved surfaces in a direction transverse to the direction inwhich is transported and minimizes any stretching of the web in thedirection in which the web is transported.

According to an aspect of the present invention, the first and secondgrooved surfaces are generally flat and converge toward each other. Asshown in FIGS. 16 and 17, the first grooved surface includes firstendless grooved belt 702 which is driven to revolve around rollers 703and 705. Second grooved surface includes endless belt 802 which isdriven to revolve about rollers 803 and 805. As shown in FIG. 17, thefirst grooved surface 702 includes projecting portions and nonprojectingportions. The second grooved surface 802 includes projecting portionsand nonprojecting portions.

As shown in FIGS. 16 and 17, roller 750 acts as a means for orientingsheet 754 on the projecting portions of the first grooved surface 702before impinging sheet 754 with the projecting portions of the secondgrooved surface 802. Roller 751 acts as an means for orienting sheet 754on projecting portions of the first grooved surface 702 after sheet 754is no longer impinged with the projecting portions of the second groovedsurface 802. Sheet 754 enters on the right side of the arrangement shownin FIG. 16 where, as shown in FIG. 17e, the projecting portions are notinterdigitated. Sheet 754 exits on the left side of the arrangementshown in FIG. 16 where, as shown in FIG. 17c the projecting portions areinterdigitated. The projecting portions gradually become interdigitatedin the right to left direction of FIG. 16.

The shape of the projecting portions and the impingement relationshipsof the embodiments shown in FIGS. 16 and 17 are preferably the same asthose in the embodiment shown and described in relation to FIGS. 1-5which uses two grooved rollers. It is preferable to transport theprojecting portions of the second grooved surface at a speed whichstretches the web between the projecting portions of the first andsecond grooved surfaces in a direction transverse to the direction inwhich is transported and minimizes any stretching of the web in thedirection in which the web is transported.

According to an aspect of the present invention, both of the first andsecond grooved surfaces are generally cylindrical and rotate about axeswhich are fixed, curved and parallel to each other. As shown in FIG. 18,the first grooved surface 902 includes a series for projecting portions904 and nonprojecting portions 906. Second grooved surface 1002 hasprojecting portions 1004 and nonprojecting portions 1006. In thisarrangement, the first and second grooved surfaces both stretch and theweb in the direction transverse to the direction in which the web istransported. Such an arrangement alleviates the need for an additionalmeans for spreading the film.

Roller 950 is a means for orienting a sheet 954 on a projecting portionsof the first grooved surface 902 before impinging sheet 954 with aprojecting portions of the second grooved surface 1002. Roller 1050 is ameans for orienting sheet 954 after sheet 954 is no longer impinged withthe projecting portions of the first grooved surface 902.

The shape of the projecting portions and the impingement relationshipsof the embodiment shown in FIGS. 18 is preferably the same as those inthe embodiment shown and described in relation to FIGS. 1-5 which usestwo grooved rollers. It is preferable to transport the projectingportions of the second grooved surface at a speed which stretches theweb between the projecting portions of the first and second groovedsurfaces in a direction transverse to the direction in which istransported and minimizes any stretching of the web in the direction inwhich the web is transported.

The inventions so far described are stretch wrapping methods andapparatus. The drawing figures and the description of the arrangementsdepicted in those drawing figures also disclose various embodiments ofmethods and apparatus which may be employed in fields of inventiondifferent and apart from the stretch wrapping methods and apparatus ofthe packaging art.

These additional fields of invention include methods and apparatus fortransverse and biaxial stretching of sheet materials which can beemployed as an integral part of the manufacturing process for producingsuch sheet materials or as a separate processing operation after sheetmaterials have been produced.

The methods and apparatus for transverse stretching of sheet materialscan be used alone to stretch the sheet materials in a directiontransverse to the direction in which they are being transported. Inaddition, these processes and apparatus for manufacturing or processingtransversely stretched sheet material can be used in combination withmethods and apparatus for manufacturing or processing longitudinallystretched sheet material to result in methods and apparatus formanufacturing or processing biaxially stretched sheet materials.

In addition to manufacturing or processing sheet material which is in aplanar form, it is possible to manufacture or process sheet materialwhich is in a tubular form or in the form of a container or series ofcontainers such as bags.

Additional advantages and modifications will readily occur to thoseskilled in the art. The invention in its broader aspect is, therefore,not limited to the specific details, representative apparatus andillustrative examples shown and described. Accordingly, departures maybe made from such details without departing from the spirit or scope ofthe general inventive concepts as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A process for stretch wrapping a load with asheet of stretch wrap packaging material comprising:introducing thesheet of stretch wrap packaging material onto tips of projectingportions of a first circumferentially grooved roller surface andspanning nonprojecting portions of the first grooved surface;transporting the sheet and the first grooved surface in a directiongenerally parallel to the grooves; impinging the sheet spanning thenon-projecting portions of the first grooved surface with tips ofprojecting portions of a second circumferentially grooved roller surfacedownstream of where the sheet of stretch wrap packaging material isintroduced onto the tips of projecting portions of the firstcircumferentially grooved roller surface; transporting the tips ofnonprojecting portions of the second grooved surface at a speed which isless than the speed of the tips of projecting portions of the firstgrooved surface; stretching the sheet between the projecting portions ofthe first and second grooved surfaces in a direction transverse to thedirection in which the sheet is transported; separating the stretchedsheet from the first and second grooved surfaces; and wrapping thestretched sheet around a load.
 2. A process for stretch wrapping a loadwith a sheet of stretch wrap packaging material comprising:transportingthe sheet of stretch wrap packaging material and stretching the sheet inthe direction in which the sheet is transported; introducing the sheetonto tips of projecting portions of a first circumferentially groovedroller surface and spanning nonprojecting portions of the first groovedsurface; transporting the sheet and the first grooved surface in adirection generally parallel to the grooves; impinging the sheetspanning the nonprojecting portions of the first grooved surface withtips of projecting portions of a second circumferentially grooved rollersurface downstream of where the sheet of stretch wrap packaging materialis introduced onto the tips of projecting portions of the firstcircumferentially grooved roller surface; transporting the tips ofprojecting portions of the second grooved surface at a speed which isless than the speed of the tips of projecting portions of the firstgrooved surface; stretching the sheet between the projecting portions ofthe first and second grooved surfaces in a direction transverse to thedirection in which the sheet is transported; separating the stretchedsheet from the first and second grooved surfaces; and wrapping thestretched sheet around a load.
 3. An apparatus for stretch wrapping aload with stretch wrap packaging material comprising:means fordispensing a sheet of stretch wrap packaging material including a firstrotatable roller with a circumferentially grooved surface havingprojecting portions with tips and nonprojecting portions fortransporting the sheet in a direction generally parallel to the grooves,a second rotatable roller with a circumferentially grooved surfacehaving projecting portions with tips which extend between the projectingportions of the first grooved surface and nonprojecting portions inwhich the projecting portions of the first grooved surface extend forimpinging and stretching the sheet in a direction transverse to thedirection in which the sheet is being transported, means for orientingthe sheet on the tips of the projecting portions of the first groovedsurface before impinging the sheet with the tips of the projectingportions of the second grooved surface, means for maintaining the tipsof the projecting portions of the second grooved surface at a speedwhich is less than the speed of the tips of the projecting portions ofthe first grooved surface; and means for providing relative rotationbetween the dispensing means and a load to wrap the stretched sheetaround the load.
 4. An apparatus for stretch wrapping a load with asheet of stretch wrap packaging material comprising:means for dispensinga sheet of stretch wrap packaging material including means fortransporting the sheet and stretching the sheet along the direction inwhich it is transported, a first rotatable roller with acircumferentially grooved surface having projecting portions with tipsand nonprojecting portions for transporting the sheet in a directiongenerally parallel to the grooves, a second rotatable roller with acircumferentially grooved surface having projecting portions with tipswhich extend between the projecting portions of the first groovedsurface and nonprojecting portions in which the projecting portions ofthe first grooved surface extend for impinging and stretching the sheetin a direction transverse to the direction in which the sheet is beingtransported, means for orienting the sheet on the tips of the projectingportions of the first grooved surface before impinging the sheet withthe tips of the projecting portions of the second grooved surface, meansfor maintaining the tips of the projecting portions of the secondgrooved surface at a speed which is less than the speed of the tips ofthe projecting portions of the first grooved surface; and means forproviding relative rotation between the dispensing means and a load towrap the stretched sheet around the load.
 5. A process for stretching asheet comprising:introducing the sheet onto tips of projecting portionsof a first circumferentially grooved roller surface and spanningnonprojecting portions of the first grooved surfaces; transporting thesheet and the first grooved surface in a direction generally parallel tothe grooves; impinging the sheet spanning the nonprojecting portions ofthe first grooved surface with tips of projecting portions of a secondcircumferentially grooved roller surface downstream of where the sheetis introduced onto the tips of projecting portions of the firstcircumferentially grooved roller surface; transporting the tips ofprojecting portions of the second grooved surface at a speed which isless than the speed of the tips of projecting portions of the firstgrooved surface; stretching the sheet between the projecting portions ofthe first and second grooved surfaces in a direction transverse to thedirection in which the sheet is transported; separating the stretchedsheet from the first and second grooved surfaces.
 6. A process forstretching a sheet comprising:transporting the sheet and stretching thesheet in the direction in which the sheet is transported; introducingthe sheet onto tips or projecting portions of a first circumferentiallygrooved roller surface and spanning nonprojecting portions of the firstgrooved surface; transporting the sheet and the first grooved surface ina direction generally parallel to the grooves; impinging the sheetspanning the nonprojecting portions of the first grooved surface withtips of projecting portions of a second circumferentially grooved rollersurface downstream of where the sheet is introduced onto the tips ofprojecting portions of the first circumferentially grooved rollersurface; transporting the tips of projecting portions of the secondgrooved surface at a speed which is less than the speed of the tips ofprojecting portions of the first grooved surface; stretching the sheetbetween the projecting portions of the first and second grooved surfacesin a direction transverse to the direction in which the sheet istransported; separating the stretched sheet from the first and secondgrooved surfaces.
 7. An apparatus for stretching a sheet comprising:afirst rotatable roller with a circumferentially grooved surface havingprojecting portions with tips and nonprojecting portions fortransporting the sheet in a direction generally parallel to the grooves;a second rotatable roller with a circumferentially grooved surfacehaving projecting portions with tips which extend between the projectingportions of the first grooved surface and nonprojecting portions inwhich the projecting portions of the first grooved surface extend forimpinging and stretching the sheet in a direction transverse to thedirection in which the sheet is being transported; means for orientingthe sheet on the tips of the projecting portions of the first groovedsurface before impinging the sheet with the tips of the projectingportions of the second grooved surface; means for maintaining the tipsof the projecting portions of the second grooved surface at a speedwhich is less than the speed of the tips of the projecting portions ofthe first grooved surface.
 8. An apparatus for stretching a sheetcomprising:means for transporting a sheet and stretching the sheet alongthe direction in which it is transported; a first rotatable roller witha circumferentially grooved surface having projecting portions with tipsand nonprojecting portions for transporting the sheet in a directiongenerally parallel to the grooves; a second rotatable roller with acircumferentially grooved surface having projecting portions with tipswhich extend between the projecting portions of the first groovedsurface and nonprojecting portions in which the projecting portions ofthe first grooved surface extend for impinging and stretching the sheetin a direction transverse to the direction in which the sheet is beingtransported; means for orienting the sheet on the tips of the projectingportions of the first grooved surface before impinging the sheet withthe tips of the projecting portions of the second grooved surface; meansfor maintaining the tips of the projecting portions of the secondgrooved surface at a speed which is less than the speed of the tips ofthe projecting portions of the first grooved surface.
 9. The process ofclaim 1, 2, 5, or 6 wherein the speed of the tips of projecting portionsof the second grooved surface is greater than the tangential speed ofthe first grooved surface at the radius where the tips of the projectingportions of the second grooved surface maximally impinge the sheet. 10.The process of claim 1, 2, 5, or 6 wherein the speed of the tips of theprojecting portions of the second grooved surface is substantially lessthan the tangential speed of the first grooved surface at the radiuswhere the tips of projecting portions of the second grooved surfacefirst impinge the sheet and substantially greater than the tangentialspeed of the first grooved surface at the radius where the tips ofprojecting portions of the second grooved surface maximally impinge thesheet
 11. The process of claim 1, 2, 5, or 6 wherein the speed of thetips of projecting portions of the second grooved surface is toward thecenter of the range between the tangential speed of the first groovedsurface at the radius where the tips of projecting portions of thesecond grooved surface first impinge the sheet and the tangential speedof the first grooved surface at the radius where the tips of projectingportions of the second grooved surface maximally impinge the sheet. 12.The process of claim 1, 2, 5, or 6 wherein the speed of the tips of theprojecting portions of the second grooved surface is approximately theaverage of the tangential speed of the first grooved surface at theradius where the tips of projecting portions of the second groovedsurface first impinge the sheet and the tangential speed of the firstgrooved surface at the radius where the tips of projecting portions ofthe second grooved surface maximally impinge the sheet.
 13. The processof claim 1, 2, 5, or 6 wherein the speed of the tips of projectingportions of the second grooved surface is approximately one half thespeed of the tips of projecting portions of the first grooved surface,times the sum ofthe radius of the second roller at the tips of theprojecting portions of the second grooved surface over the radius of thefirst roller at the tips of the projecting portions of the first groovedsurface, and the radius of the second roller at the tips of theprojecting portions of the second grooved surface over the differencebetween the center distance of the grooved rollers and the radius of thesecond roller at the tips of the projecting portions of the secondgrooved surface
 14. The apparatus of claim 3, 4, 7, or 8 wherein themaintaining means maintains the tips of projecting portions of thesecond grooved surface at a speed greater than the tangential speed ofthe first grooved roller at the radius where the tips of projectingportions of the second grooved roller maximally impinge the sheet. 15.The apparatus of claim 3, 4, 7, or 8 wherein the maintaining meansmaintains the tips of projecting portions of the second grooved surfaceat a speed substantially less than the tangential speed of the firstgrooved surface at the radius where the tips of projecting portions ofthe second grooved surface first impinge the sheet and substantiallygreater than the tangential speed of the first grooved surface at theradius where the tips of projecting portions of the second groovedsurface maximally impinge the sheet.
 16. The apparatus of claim 3, 4, 7,or 8 wherein the maintaining means maintains the tips of projectingportions of the second grooved surface at a speed is toward the centerof the range between the tangential speed of the first grooved surfaceat the radius where the tips of projecting portions of the secondgrooved surface first impinge the sheet and the tangential speed of thefirst grooved surface at the radius where the tips of projectingportions of the second grooved surface maximally impinge the sheet. 17.The apparatus of claim 3, 4, 7, or 8 wherein the maintaining meansmaintains the tips of the projecting portions of the second groovedsurface at a speed which is approximately the average of the tangentialspeed of the first grooved surface at the radius where the tips ofprojecting portions of the second grooved surface first impinge thesheet and the tangential speed of the first grooved surface at theradius where the tips of projecting portions of the second groovedsurface maximally impinge the sheet.
 18. The apparatus of claim 3, 4, 7,or 8 wherein the maintaining means maintains the tips of projectingportions of the second grooved surface at a speed which is approximatelyone half the speed of the tips of projecting portions of the firstgrooved surface, times the sum ofthe radius of the second roller at thetips of the projecting portions of the second grooved surface over theradius of the first roller at the tips of the projecting portions of thefirst grooved surface, and the radius of the second roller at the tipsof the projecting portions of the second grooved surface over thedifference between the center distance of the grooved rollers and theradius of the second roller at the tips of the projecting portions ofthe second grooved surface.
 19. The apparatus of claim 3, 4, 7 or 8wherein the projecting portions have sides which converge outwardly atan angle in the range of about 50 to 90 degrees.
 20. The apparatus ofclaim 3, 4, 7 or 8 wherein the projecting portions have sides whichconverge outwardly at an angle in the range of about 10 to 20 degrees.21. The apparatus of claim 3, 4, 7 or 8 wherein the projecting portionshave flat sides.
 22. The apparatus of claim 3, 4, 7 or 8 wherein theprojecting portions have a shape which supports less than about 20% ofthe sheet on the projecting portions along the direction transverse tothe grooves and leaves more than about 80% of the sheet widthunsupported and available for stretching along the direction transverseto the grooves.
 23. The apparatus of claim 3, 4, 7 or 8 wherein theprojecting portions have a shape which supports less than about 15% ofthe sheet on the projecting portions along the direction transverse tothe grooves and leaves more than about 85% of the sheet widthunsupported and available for stretching along the direction transverseto the grooves.
 24. The apparatus of claim 3, 4, 7 or 8 wherein theprojecting portions have a shape which supports less than about 10% ofthe sheet on the projecting portions along the direction transverse tothe grooves and leaves more than about 90% of the sheet widthunsupported and available for stretching along the direction transverseto the grooves.
 25. The apparatus of claim 3, 4, 7 or 8 wherein thedistance between the tips of the projecting portions of the firstgrooved surface is in the range of about 1/8 to 1/2 inches.
 26. Theapparatus of claim 3, 4, 7 or 8 wherein the distance between the tips ofthe projecting portions of the first grooved surface is in the range ofabout 1/4 to 3/8 inches.
 27. The apparatus of claim 3, 4, 7 or 8 whereinthe tip sharpness radius of the projecting portions is in the range ofabout 1/128 to 1/16 inches.
 28. The apparatus of claim 3, 4, 7 or 8wherein the tip sharpness radius of the projecting portions is in therange of about 1/64 to 1/32 inches.
 29. The apparatus of claim 3, 4, 7or 8 wherein the maximal impingement is in the range of a 1/8 to 1inches.
 30. The apparatus of claim 3, 4, 7 or 8 wherein the maximalimpingement is in the range of about 1/4 to 1/2 inches.
 31. Theapparatus of claim 3, 4, 7 or 8 wherein the maximal impingement issubstantially greater than the distance between the tips of theprojecting portions of the first grooved surface.
 32. The apparatus ofclaim 3, 4, 7 or 8 wherein the maximal impingement is in the range ofabout twice the distance between the tips of the projecting portions ofthe first grooved surface.
 33. The apparatus of claim 3, 4, 7 or 8wherein the tip sharpness radius of the tips is in the range of about 3to 33% of the distance between the tips of the projecting portions ofthe first grooved surface.
 34. The apparatus of claim 3, 4, 7 or 8 wherethe tip sharpness radius of the tips is in the range of about 6 to 12%of the distance between the tips of the projecting portions of the firstgrooved surface.
 35. The apparatus of claim 3, 4, 7 or 8 including meansfor spreading the sheet in the transverse direction after stretching thesheet in the transverse direction.
 36. The apparatus of claim 3, 4, 7 or8 including a bowed roller which rotates about a fixed curved axis forspreading the sheet in the transverse direction after stretching thesheet in the transverse direction.
 37. The apparatus of claim 3, 4, 7 or8 wherein the first and second grooved surfaces are bowed rollers whichrotate about fixed curved axes for both stretching and spreading thesheet in the transverse direction.
 38. The apparatus of claim 3, 4, 7 or8 wherein the second grooved surface includes a plurality of surfacesfor sequentially impinging the sheet to increasing extents.
 39. Theapparatus of claim 3, 4, 7 or 8 wherein the second grooved surfaceincludes a plurality of circumferentially grooved rollers forsequentially impinging the sheet to increasing extents.
 40. Theapparatus of claim 3, 4, 7 or 8 including means for separating the sheetfrom one of the grooved surfaces after the sheet has been stretched inthe transverse direction.
 41. The apparatus of claim 3, 4, 7 or 8including belts which circulate around the projecting portions of one ofthe grooved surfaces and a location spaced from the grooved surface forseparating the packaging material from said one of the grooved surfacesafter the packaging material has been stretched in the transversedirection.
 42. The process of claim 5 or 6 wherein the step ofintroducing a sheet includes introducing a flattened tubular sheet ontotips of projecting portions of the first grooved surface and spanningnonprojecting portions of the first grooved surface.
 43. The process ofclaim 5 or 6 wherein the step of introducing a sheet includesintroducing a flattened bag onto tips of projecting portions of a firstgrooved surface and spanning nonprojecting portions of the first groovedsurface.
 44. The process of claims 1, 2, 5 or 6 wherein the transportingsteps include transporting the tips of the projecting portions of thefirst and second grooved surfaces at respective speeds which minimizeany stretching of the sheet in the direction in which the sheet istransported while the sheet is being stretched between the groovedsurfaces in a direction transverse to the direction in which the sheetis transported.
 45. The apparatus of claims 3, 4, 7 or 8 wherein themaintaining means maintains the tips of the projecting portions of thefirst and second grooved surfaces at respective speeds which minimizeany stretching of the sheet in the direction in which the sheet istransported while the sheet is being stretched between the groovedsurfaces in a direction transverse to the direction in which the sheetis transported.